1. Field of Invention
This invention relates to the production, purification, and isolation of hydroxyamides, which are useful as chemical intermediates and chemical crosslinkers.
2. Description of Prior Art
Hydroxyamides have been synthesized by the aminolysis of dimethyl esters by alkanolamines. Isolation and purification of solid hydroxyamide products is done conventionally either by recrystallization (J. Coat. Tech., 50 (643), 49-55 (1978); U.S. Pat. Nos. 4,032,460; 4,076,917; 4,493,909; 4,727,111; Japanese Patent 56-062895) or by prilling/flaking. Using recrystallization, relatively pure product is obtained but product losses due to dissolution in the solvents used and the complexity of removing residual solvent from the product as well as recovering solvents for reuse pose significant disadvantages to this approach. Recrystallization is typically performed by dissolving the crude hydroxyamide in solvent, such as methanol/acetone, cooling to grow the crystals, filtering the product away from the mother liquors, and drying the product free of residual solvent. Alternatively, recrystallization may entail adding solvent to melted hydroxyamide, followed by crystal growth, filtration, and drying as described above.
Prilling/flaking requires that the hydroxyamide be maintained in a fluid state for several hours until the operation is complete. During this time in the molten state some of the product degrades to undesirable byproducts.
The physical state of the crude hydroxyamides of interest is that of a soft, sticky, waxy solid, which typically renders the materials unsuitable for use in powder coatings, such use requiring free-flowing powders. Certain hydroxyamides are useful as crosslinkers in powder coatings based on polyester or acrylate chemistries.